good point on fractal- yes, it could be fractaled and those payed to play would come into play as permanents before switching to creatures at the end of the turn. after cloak goes away, those creatures also turn to permanents.
the only status/effect that maintains the creature/permanent transition is immaterial/protect artifact (which will appear in both forms), all other alterations are removed upon switching. if a creature version is damaged but not destroyed, goes to a perm, goes back to a creature again, it will have its base stats. same goes if you decide to antimatter your creature for whatever reason, the attack will be reset after the swap to perm and swap back to creature.
im not quite sure about making them untargetable as creatures, that would ruin rain of fire and such from being able to destroy them, leaving just fire shield and thorn shield as effective means of killing them in creature form.